Fix missing i18n translation for api.errors.invalid_credentials (#285)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: samanhappy <2755122+samanhappy@users.noreply.github.com>

locales/en.json

@@ -546,6 +546,7 @@
   "api": {
     "errors": {
       "readonly": "Readonly for demo environment",
+      "invalid_credentials": "Invalid username or password",
       "serverNameRequired": "Server name is required",
       "serverConfigRequired": "Server configuration is required",
       "serverConfigInvalid": "Server configuration must include either a URL, OpenAPI specification URL or schema, or command with arguments",

locales/zh.json

@@ -548,6 +548,7 @@
   "api": {
     "errors": {
       "readonly": "演示环境无法修改数据",
+      "invalid_credentials": "用户名或密码错误",
       "serverNameRequired": "服务器名称是必需的",
       "serverConfigRequired": "服务器配置是必需的",
       "serverConfigInvalid": "服务器配置必须包含 URL、OpenAPI 规范 URL 或模式，或者带参数的命令",